Still trying to figure that out, nine years after retiring. Comes down to what you want to do.
Wife wanted to travel, road trips. RV works for that. She just died, so the question is open again.
Do you want to fish a particular lake? A boat that fits that lake.
Do you want to cruise rivers? Then a boat that is more like a floating RV.
Do you want to travel the world, visiting only the coasts? There are boats that will do that, but bring lots of money, no RV costs that much, and it would be less expensive to book yourself full time on cruise ships.
I think if I would have a boat, it would be used like a RV, cruising the inland waterways. But it would cost about 4-10 times as much to move as a RV following the roads along those waterways, so I'm inclined to stay with the RV.